22 THE DESIGN OF AN OIL ENGINE. 
mental data and from a theoretical consideration of points in the design as affected 
by this experimental data. 
If these three assumptions are justifiable, there should be no hesitation on the 
part of a well-organized engine-designing force to undertake the design of an oil 
engine to fill a certain requirement. Attempt has been made to emphasize this 
matter strongly. Experience is a wonderful guide, and the author would be the 
last to decry its value. However, it seems, in view of the newness of the oil engine 
as a commercial machine, and in view of the fact that all who are interested in 
this matter are too apt to be partisan advocates of one type or another, that an en- 
gine designed under this method might offer advantages which the product of some 
exploiting firm would lack. It is not claimed that the author is an impartial per- 
son. Quite the reverse is true. But it is hoped that this paper may be considered 
from an engineering viewpoint, each one having the privilege of rejecting those 
points which reflect the enthusiasm of the author or, rather, of making such al- 
lowance for these individual ideas as may seem wise and of considering how the 
paper as a whole may be used as a guide for such designs. It will be a long time 
before these matters of type are settled to the satisfaction of all. For this reason 
it is perfectly proper for the author to present his individual opinions, believing 
them to be best. At the same time this paper does not depend upon these theories, 
but is rather an attempt to handle the whole matter on such a basis that changes in 
this design to eliminate these individual theories would not affect the work of han- 
dling the new design in the draughting room. It would simply mean new allowances 
for changes in method of operation in the engine. 
Under the head of general data there are several points to be settled before the 
design is begun. They are at present largely a matter of judgment. There are 
apparent reasons for following certain designs. These will be given as they appear 
to the author. Owing to the newness of the oil engine these claims of supremacy 
cannot be positively stated as facts, but good reasons can be given for their adoption. 
The general features to be decided upon before the actual design is begun are 
as follows :— 
1. The type, whether two-cycle or four-cycle. 
2. The pressure of compression, and whether this pressure shall be constant 
or not. 
3. The class of fuel to be used, and what steps shall be taken to insure its suc- 
cessful use. 
4. The means for starting, and what, if any, steps are needed to make practi- 
cal the particular type of starting settled upon. 
5. The best arrangement of the air compressor. 
6. The peculiar qualities necessary in fuel valve and fuel pump. 
TYPE. 
The type selected was four-cycle and the engine designed for naval use. The 
Navy needs two speeds; one is a normal economical cruising speed and the other a 
maximum possible speed, regardless of economy. 
